Procedural Content Generation (PCG) is a technique to generate complex and diverse environments in an automated way.

Procedural Content Generation (PCG) is a technique to generate complex and diverse environments in an automated way.

Procedural Content Generation via Reinforcement Learning (PCGRL) offers a method for training controllable level designer agents without the need for human datasets, using metrics that serve as proxies for level quality as rewards. Existing PCGRL research focuses on single generator agents, but are bottlenecked by the need to frequently recalculate heuristics of level quality and the agent's need to navigate around potentially large maps. By framing level generation as a multi-agent problem, we mitigate the efficiency bottleneck of single-agent PCGRL by reducing the number of reward calculations relative to the number of agent actions. We also find that multi-agent level generators are better able to generalize to out-of-distribution map shapes, which we argue is due to the generators' learning more local, modular design policies. We conclude that treating content generation as a distributed, multi-agent task is beneficial for generating functional artifacts at scale.

Abstract--In recent years, the generation of diverse game levels has gained increasing interest, contributing to a richer and more engaging gaming experience. A number of level diversity metrics have been proposed in literature, which are naturally multi-dimensional, leading to conflicted, complementary, or both relationships among these dimensions. However, existing level generation approaches often fail to comprehensively assess diversity across those dimensions. This paper aims to expand horizons of level diversity by considering multi-dimensional diversity when training generative models. We formulate the model training as a multi-objective learning problem, where each diversity metric is treated as a distinct objective. Furthermore, a multi-objective evolutionary learning framework that optimises multiple diversity metrics simultaneously throughout the model training process is proposed. Our case study on the commonly used benchmark Super Mario Bros. demonstrates that our proposed framework can enhance multi-dimensional diversity and identify a Pareto front of generative models, which provides a range of tradeoffs among playability and two representative diversity metrics, including a content-based one and a player-centered one. Such capability enables decision-makers to make informed choices when selecting generators accommodating a variety of scenarios and the diverse needs of players and designers. Impact Statement--Artificial intelligence-generated content (AIGC) techniques offer a new paradigm of content creation and have numerous applications in several industry sectors, including digital games. Evaluating game levels is crucial and should consider different aspects, with diversity being one of the most important. Multiple content-based and player-centered metrics have been proposed for measuring level diversity.

The issue is that structured objects must satisfy hard requirements (e.g., molecules must be chemically valid) that are difficult to acquire

We thank all the reviewers for their careful reviews. None of these follow trivially from Xu et al. In molecule generation, validity is encouraged using the reward-based approach of MolGANs, not the SL. We will clarify this in the discussion. Thank you, we were not aware of this link.

After many years of development, quantum computing hardware is rapidly developing towards commercialization. This has led to an explosion of interest in quantum algorithms and applications [1]. In the games industry the intersection of quantum computing and games has been explored for almost a decade [2]. Although most examples are currently within an educational context [3], the potential of quantum computing for procedural generation has started to be explored [4-7]. Here we go beyond this previous proof-of-principle work by developing an example of quantum procedural generation that can provide real-time generation of levels within a live game. Specifically, we explore a generative system based on Quantum Reservoir Computing (QRC) [8] to generate game levels.

Expressive range analysis is a visualization-based technique used to evaluate the performance of generative models, particularly in game level generation. It typically employs two quantifiable metrics to position generated artifacts on a 2D plot, offering insight into how content is distributed within a defined metric space. In this work, we use the expressive range of a generator as the conceptual space of possible creations. Inspired by the quality diversity paradigm, we explore this space to generate levels. To do so, we use a constraint-based generator that systematically traverses and generates levels in this space. To train the constraint-based generator we use different tile patterns to learn from the initial example levels. We analyze how different patterns influence the exploration of the expressive range. Specifically, we compare the exploration process based on time, the number of successful and failed sample generations, and the overall interestingness of the generated levels. Unlike typical quality diversity approaches that rely on random generation and hope to get good coverage of the expressive range, this approach systematically traverses the grid ensuring more coverage. This helps create unique and interesting game levels while also improving our understanding of the generator's strengths and limitations.

Procedurally generated levels created by machine learning models can be unsolvable without further editing. Various methods have been developed to automatically repair these levels by enforcing hard constraints during the post-processing step. However, as levels increase in size, these constraint-based repairs become increasingly slow. This paper proposes using explainability methods to identify specific regions of a level that contribute to its unsolvability. By assigning higher weights to these regions, constraint-based solvers can prioritize these problematic areas, enabling more efficient repairs. Our results, tested across three games, demonstrate that this approach can help to repair procedurally generated levels faster.